The invention relates to a fuel injection nozzle for an air-compression internal-combustion engine of the type having a plurality of nozzle holes through which fuel is injected against the boundary wall of a combustion trough arranged in a piston. The volume of the combustion trough is predetermined based upon the compression ratio and the piston stroke volume.
Experimental results relating to the combustion cycle and emission behavior of a direct-injection internal-combustion engine are known from an article in SAE Paper 80 09 86 by Masahiko Hori and Hiromi Sugiyama, titled "Combined Measurement by Photography and Gas Sampling for Combustion Analysis in a Diesel Engine Cylinder." For this purpose, the distribution of the fuel/air mixture and the flame propagation as a function of the compression and of the dimensions of the combustion chamber is detected by photographic methods and the emission is analyzed as to its composition, whereby discoveries are made as to how far air movements in the combustion chamber influence the combustion process.
An internal-combustion engine with a reciprocating piston is known from German Offenlegungschrift (Published Unexamined Patent Application) No. 26 52 662, with which piston an inlet nozzle is associated which sprays fuel up to an angle of 20.degree. onto the wall of the combustion trough accommodated by the piston. Although the combustion trough accommodated by the piston is determined in its dimensions, nevertheless no instructions as to a determination of the number of the nozzle holes can be obtained from this disclosure.
An object of the invention is to optimize the number of the nozzle holes in the context of combustion trough parameters in the case of a fuel injection nozzle associated with the combustion trough.
This object is achieved according to the invention by providing an arrangement wherein the number of nozzle holes required for optimum combustion is determined and arranged in the nozzle according to the relationship ##EQU1## with Z=number of nozzle holes of the fuel injection nozzle,
D=diameter of the combustion trough in the region of the fuel contact with the boundary wall of the combustion trough in mm, PA1 H=depth of the combustion trough in mm, PA1 K=dimensionless constant which describes the qualitative value of the spin number of the combustion air on entering the combustion trough, and assumes the value 1.0 for combustion air entering the combustion trough without spin and assumes the value equal to or less than 1.5 for combustion air entering the combustion trough with spin PA1 [. . . ]=signifies a smaller integer determined from the relation or the integral portion of the number. PA1 K=dimensionless constant which assumes the value 1.0 for combustion air entering the combustion trough without a spin and a value equal to or less than 1.5 for combustion air entering the combustion trough with spin, PA1 [. . . ]=signifies a smaller integer determined from the relation of the integral portion of the number, and PA1 c=is a constant which is determinable by the relation .pi./H=0.13 mm.sup.-1 where H=24 mm. PA1 K.sub.1 . . . as dimensionless trough fractions of compression volume PA1 H . . . depth of the combustion trough in mm PA1 .epsilon. . . . compression ratio, and PA1 K.sub.2 . . . a volume ratio for an insert accommodated by the combustion trough.
In certain preferred embodiments of the invention where the combustion trough depth is 24 mm (millimeters), the number of the nozzle holes is determinable according to the relation ##EQU2## with D=diameter of the combustion trough in the region of the fuel contact with the boundary wall of the combustion trough in mm,
In certain preferred embodiments of the invention, the diameter D of the combustion trough is determinable by the relation ##EQU3## with V.sub.h . . . as stroke volume of a cylinder in mm.sup.3
By utilizing the arrangement according to the invention, it is possible for the first time to optimally determine and arrange the number of the nozzle holes of a fuel injection nozzle as a function of the combustion trough diameter, whereby the requirements of a uniform fuel distribution in the combustion chamber of the internal-combustion engine and a constant atomization into the smallest possible droplets are fulfilled. Due to the more uniform fuel distribution and atomization in the combustion chamber into the greatest possible number of small droplets a virtually homogeneous mixture is produced, which leads to a more uniform temperature distribution during combustion in the combustion chamber. Since the evolution of nitric oxide increases superproportionately with the temperature, a homogeneous temperature distribution leads to a lower nitric oxide emission.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing which show, for purposes of illustration only, an embodiment in accordance with the present invention.